In addition to my iMac, Mac Mini, and currently dead iBook, I now have a hackintosh: a dell optiplex GX620.
The specs are:
Pentium D 3.2 ghz (SSE3)
2GB RAM
200GB HD SATA
GMA950
PATA DVD-RW
USB 2
Ac'97 audio
I installed 10.5.6 on it and it works like a charm. Audio needed a simple fix, and soon i was up & running. What I did was follow the instructions in the Hardware Compatibililty List 10.5.6.
Runs great, really fast, next step is a dual boot with Linux.
Downsides? No easy path to 10.5.7, no handles on my box, slow IGP and upgrading to a Geforce 7300GT requires a reinstall.
That's another next-step: a Geforce graphics chip.
Overall, it worked fine, installed in less than an hour, by an hour's time it was fully working with audio and everything. For those scared of headaches and huge frusturation: so long as you have at least a 90% compatible machine and the abililty to buy compatibility (say USB wifi or Ethernet or audio) for the rest, it'll work fine.
Researching what amount of Mac i'd be able to get for comparable money, probably a 1ghz emac.